The present invention relates to a method and apparatus for adjusting an ink supply amount for a printing press, which adjust the amount of ink to be supplied to a plate by adjusting setting of the opening amount of an ink fountain key and the feed rate (rotation amount) of an ink fountain roller.
A four-color rotary printing press shown in FIG. 16 has printing units 9-1 to 9-4 provided for four ink colors. An ink supply unit shown in FIG. 15 is provided in each of the printing units 9-1 to 9-4.
The ink supply unit shown in FIG. 15 has an ink fountain 1, an ink 2 stored in the ink fountain 1, an ink fountain roller 3, a plurality of ink fountain keys 4 (4-1 to 4-n) aligned in the axial direction of the ink fountain roller 3, an ink ductor roller 5, an ink roller group 6, a plate 7, and a plate cylinder 8.
In the printing press having the above arrangement, the amount of ink to be supplied from the ink fountain 1 to the ink fountain roller 3 is adjusted by adjusting the opening amounts of the ink fountain keys 4. The amount of ink to be supplied from the ink fountain roller 3 to the plate 7 through the ink roller group 6 is adjusted by adjusting the feed rate (rotation amount) of the ink fountain roller 3. A print sheet is printed with the ink finally supplied to the plate 7.
The opening amount of each ink fountain key 4 is set in accordance with the image area ratio of each of areas, corresponding to the ink fountain keys 4, of the plate 7 by following the “conversion curve of the image area ratio to the opening amount of the ink fountain key” stored in advance. The feed rate of the ink fountain roller 3 is set in accordance with a predetermined reference ink feed rate. The opening amounts of the ink fountain keys 4 and the feed rate of the ink fountain roller 3 (ink feed rate) are set in units of printing units 9-1 to 9-4. More specifically, the “conversion curve of the image area ratio to the opening amount of the ink fountain key” and the reference ink feed rate are determined in units of ink colors.
Conventionally, since the “conversion curve of the image area ratio to the opening amount of the ink fountain key” and the reference ink feed rate are uniquely determined by the printing machine manufacturer, differences in standard density among the printing companies and differences depending on the environment are not considered. For this reason, the operator of each printing company actually checks the color of the printed printing product after the opening amounts of the respective ink fountain keys 4 and the feed rate of the ink fountain roller 3 are set by using the standard characteristics in units of printing units 9-1 to 9-4.
In accordance with the result of color checking, the operator finely adjusts the opening amounts of the ink fountain keys 4 separately, or the feed rate of the ink fountain roller 3, thereby dealing with the differences in standard density and the differences depending on the environment. This fine adjustment of the amount of ink to be supplied requires a very advanced technique and can be performed only by a skilled operator. The fine adjustment takes a very long period of time, leading to a delay in printing operation.
Also, conventionally, the “conversion curve of the image area ratio to the opening amount of the ink fountain key” and the reference ink feed rate must be stored in units of ink colors, and a very large memory capacity is accordingly necessary.